Mozart’s Die Zauberflöte was not performed complete in Paris until 1829, 38 years after its first performance. But in 1801, much of the score had been included in Les Mystères d’Isis, an adaptation for the Opéra de Paris by the Bohemian composer and horn player Ludwig Wenzel Lachnith, with a new French text by Étienne Morel de Chédeville.

Lachnith and his librettist preserved the general outlines of the scenario that Emanuel Schikaneder devised for Mozart, but they adapted both it and the score to fulfil the expectations of opera audiences in the French capital at that time. The two acts of the original became four, the spoken dialogue of the Singspiel was replaced by orchestral recitative, and most of the characters had their names changed – only Pamina and Sarastro (as Zarastro) remain recognisable from the original cast list. The musical changes were even more radical, with many numbers reordered, reassigned, rewritten or transposed. The Queen of Night, now called Myrrène, becomes a mezzo instead of a coloratura soprano, and the role of Papagena (as Mona) is much more substantial than before.

Elements of an 18th-century pasticcio, a new work made up from existing compositions, were incorporated as well, though apart from the Adagio from Haydn’s Symphony No 103, which is used to open the fourth act, all of Lachnith’s borrowings are taken from other operas by Mozart – from La Clemenza di Tito, Le Nozze di Figaro and Don Giovanni. Some of those reworkings seem startling to modern ears – Sesto’s Parto, Parto, from Clemenza di Tito, is transformed into a duet for Isménor and Bochoris (AKA Tamino and Papageno); Don Giovanni’s Champagne Aria becomes a trio for Pamina, Bochoris and Mona; while Myrrène may lose the Queen of Night’s second aria, she gains Donna Anna’s first aria from Don Giovanni (transposed down) and Vitellia’s Non più di Fiori from Clemenza.

Some of these juxtapositions may be a bit disconcerting at times, and in the end Les Mystères d’Isis remains just a curiosity, but a historically significant one, for the success of Lachnith and De Chédeville’s adaptation paved the way for more of Mozart’s operas to be heard in Paris over the following decade. The performance by the period instruments of Le Concert Spirituel, conducted with great verve by Diego Fasolis, has real freshness about it, too. Chantal Santon-Jeffery is the fresh-voiced Pamina, Renata Pokupić the fire-breathing Myrrène, while Jean Teitgen is the suitably assertive Zarastro. Mozart purists may hate it, but really it’s a lot of fun.